The present invention relates to a clutch cover assembly, particularly to a clutch cover assembly with a mechanism for keeping a pressing load constant by compensating for the wear on the friction members.
A clutch cover assembly is, generally, fixed to a flywheel of the engine and presses friction members of the clutch disc assembly against the flywheel in order to transmit the power of the engine to the transmission. Excessive wear on the friction members shortens the lives of the clutch disc assembly and the clutch disc assembly. It is possible to lengthen life of the clutch disc assembly by increasing effective thickness of friction members. For example, by attaching facings to the cushioning plate without using rivets.
The clutch cover assembly disclosed in Japanese Patent Laying-Open No. 27092/1998 maintains the pressing load of the diaphragm spring at its initial value as facings wear. This clutch cover assembly is shown in FIG. 10 and has a pressure plate 151 formed with an annular groove 152 in which a diaphragm spring posture maintenance mechanism 153 is arranged. The mechanism 153 comprises both an outer fulcrum ring 155 and an inner fulcrum ring 156 against which the outer periphery of the diaphragm spring 154 presses, slide keys 157 and 158 located between the fulcrum rings 155 and 156, and the grooved pressure plate. Both slide keys 157 and 158 are formed with an inclined surface such that axial height decreases radially outward. The fulcrum rings 155 and 156 are formed with inclined surfaces conforming to the inclined surfaces of the slide keys 157 and 58. The slide keys 157 and 158 are urged radially outward by springs 159 and 160, respectively.
The inner fulcrum ring 156 is moved toward the diaphragm spring 154 by the spring 160 and the slide keys 158 as facings 161 wear. Upon release, both fulcrums 155 and 156 move in concert, thus the posture of the diaphragm spring 154 and the pressing load of the diaphragm spring 154 is maintained at the initial value.
In the above-mentioned structure, it is necessary to form the groove 152 in the lateral surface of the pressure plate 151 to contain the spring posture maintenance mechanism 153. The groove 152 is difficult to fashion, deviation thus complicating accurate and correspondent movement of the fulcrum rings 155 and 156, affecting amount of wear on the facings 161. Therefore, design requirements make it difficult to maintain the initial pressing load of the diaphragm spring 154.
The above-mentioned structure is further affected when the engine rotation speed rlses, applying centrifugal force to the slide keys 157 and 158, thus making the slide keys move radially outward. In this case, even though the facings 161 are not worn, the slide keys 157 and 158 move so as to move the fulcrum rings 155 and 156 axially. As a result, it is impossible to maintain the posture of the initial pressing load of the diaphragm spring 154.